Cryogenic cycle and apparatus

ABSTRACT

AN APPARATUS SUITABLE FOR DEVELOPING CRYOGENIC TEMPERATURES. INCOMING HIGH-PRESSURE FLUID IS EXPANDED AND FURTHER COOLED AFTER BEING INITIALLY COOLED BY HEAT EXCHANGE WITH RETURNING LOW-PRESSURE FLUID. AT LEAST A PORTION OF THE WORK DEVELOPED IN THE EXPANDER IS EXTRACTED BY COMPRESSING A FLUID WHICH IS CIRCULATED BACK AND FORTH BETWEEN THE EXPANSION CHAMBER AND A BALANCING CHAMBER IN WHICH THE COMPRESSION TAKES PLACE. MEANS ARE PROVIDED TO REMOVE THE HEAT OF COMPRESSION THROUGH HEAT EXCHANGE.

Oct. 19, "1 97] w. H. HOGAN ETA!- 3,513,335

' CRYOGENIC CYCLE AND APPARATUS Filed June 12, 1969 6 Sheets-Sheet 1 32 3| 30 Fig. 1

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w. H. HOGAN CRYOGENIC CYCLE AND APPARATUS Oct. 19, 1971 Filed June 12, 1969 I. o w W m w a w M w H. Tltlltll. w f w (U 2 4 Walter H. Hogan Robert W. Stuart INVENTORS /lM-k Attorney 6 Sheets-Sheet 4 w. H. HOGAN ETA!- CRYOGENIC CYCLE AND APPARATUS Oct. 19; 1971 Filed June 12, 1969 INVENTORS Attorney Wol'rer H.Hogon Robert W. Sruori Fig. 10

Oct. 19, 1971 w, HOGAN ETAL 3,613,385

CRYOGENIC CYCLE AND APPARATUS Filed June 12, 1959 6 Sheets-Sheet 5 ii I43 I h Fig. 11

Walter H. Hogan RoberfW. Sruorf INVENTORS Vida/ W Attorney Oct. 19, 1971 W. H. HOGAN ETA]- CRYOGENIC CYCLE AND APPARATUS Filed June 12, 1969 WWW 6 Sheets-Sheet 6 lee- I87 I73 g ies I96 g 5 "I86 I95 I90 I Flg. 12

Walter H.'Hogon Robert W. Siuorr INVENTORS Airorney United States Patent 3,613,385 CRYOGENIC CYCLE AND APPARATUS Walter H. Hogan, Wayland, and Robert W. Stuart, Wakefield, Mass., assignors to Cryogenic Technology, Inc.,

Waltharn, Mass.

Filed June 12, 1969, Ser. No. 832,752 Int. Cl. F25b 9/00 US. Cl. 62-6 29 Claims ABSTRACT OF THE DESCLOSURE An apparatus suitable for developing cryogenic temperatures. Incoming high-pressure fluid is expanded and further cooled after being initially cooled by heat exchange with returning low-pressure fluid. At least a portion of the work developed in the expander is extracted by compressing a fluid which is circulated back and forth between the expansion chamber and a balancing chamber in which the compression takes place. Means are provided to remove the heat of compression through heat exchange.

This invention relates to cryogenic cycles and apparatus, and more particularly to a cryogenic cycle and apparatus which combines the desirable features of the Claude or Brayton cycle with those of the Gifford-McMahon cycle.

There are, of course, several well-known cycles for developing cryogenic temperatures, and among these one of the most efiicient is the so-called Claude or Brayton cycle. Probably the most successful embodiment of this cycle is the socalled Collins cryostat (see, for example, U.S. Pats. 2,458,894 and 3,250,079). The efficiency of this cycle is due at least in part to the use of a circulating fluid stream in an apparatus using indirect heat exchange in which the void volumes are minimized. However, since work is extracted from the fluid to attain low temperatures, it is necessary to provide means for dissipating or extracting the work. This, in turn, requires a large crankshaft or the like with large bearings and their associated wear problems.

Another well-known cycle generally referred to as the Gifford-McMahon cycle (see, for example, U.S. Pats. 2,906,101; 2,966,034 and 2,966,035) avoids the major problems associated with work extraction. It does this through the use of regenerators and a unique method of introducinghigh-pressure fluid and exhausting initiallycooled fluid into a low-pressure reservoir. In fact, the socalled no-work cycle removes most of the energy from the fluid in the form of heat, and thus minimizes the amount of mechanical work extraction which must be performed. However, since this apparatus requires one or more regenerators in the fluid flow path it must of necessity introduce void volumes which may be generally defined as those spaces which are required for clearances and gas passages, and which do not contribute to the development of refrigeration through the expansion of highpressure fluid.

It would, therefore, be desirable to have a cryogenic cycle and apparatus which minimize the difficulties concerned with work extraction and which at the same time attain a high efficiency such as that associated with the Claude or Brayton cycle and apparatus. The cycle and apparatus of this invention attain these desiderata by combining the Claude and Gifford-McMahon cycles in a way to provide in the apparatus a balancing fluid chamber which acts in the role of a compressor to extract or absorb energy developed. A flow path is provided between a balancing chamber and a refrigerating chamber, the flow path incorporating a heat storage means (regenerator) to minimize the thermal losses associated with the fluid circulation. Heat exchange means are also provided to remove 3,613,385 Patented Oct. 19, 1971 the heat of compression from the fluid in the balancing chamber. The resulting cycle and apparatus achieve the reliability of the Gifford-McMahon engine and the flexibility and efliciency of the Claude engine. The apparatus lends itself to staging, to integration with other cryogenic equipment such as a Joule-Thomson loop, and to the use of various driving means.

It is, therefore, a primary object of this invention to provide an improved cryogenic cycle and apparatus which achieve a high degree of reliability along with high efficiency. It is another object of this invention to provide an apparatus of the character described which requires relatively simple and small Work extraction means and hence an apparatus which is capable of operating over an extended length of time without servicing. It is yet another object of this invention to provide an improved cryogenic refrigerator which, when staged, can be combined with a Joule-Thomson loop to provide a simple, reliable and eflicient hydrogen or helium liquefier. Other objects of the invention will in part be obvious and will in part be apparent hereinafter.

The invention accordingly comprises the several steps and relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combination of elements and arrangement of parts which are adapted to effect such steps, as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawings in which FIG. 1 is a diagrammatic representation of the simplest embodiment of a refrigerator constructed in accordance with this invention and incorporating a mechanical drive and a flow path between the two chambers external of the housing;

FIG. 2 is a series of diagrammatic representations of the refrigerator showing a portion of the apparatus of FIG. 1 and illustrating the steps in the refrigeration cycle of this invention;

FIG. 3 is a tabulation of the operation of the fluid control means;

FIG. 4 is a PV diagram illustrative of one mode of operation of the apparatus of FIG. 1;

FIG. 5 is an embodiment in which the flow path between the balancing and expansion chambers is located within the displacer;

FIG. 6 illustrates the apparatus of FIG. 1 with one embodiment of a pneumatic driving means;

FIG. 7 illustrates the apparatus of FIG. 5 with another embodiment of pneumatic driving means and adapted for an open cycle;

FIG. 8 illustrates another embodiment of a mechanically driven refrigerator;

FIG. 9 illustrates one embodiment of the adaptation of the refrigerator of FIG. 5 to staging;

FIG. 10 illustrates another embodiment of the adaptation of the refrigerator of FIG. 5 to staging;

FIG. 11 illustrates one embodiment of the integration of a Joule-Thomson loop with the refrigerator of FIG. 10 to form a very low temperature refrigerator or a liquefler; and

FIGS. 12 and 13 illustrate two other embodiments of staged refrigerators using aligned displacers within a single housing.

FIG. 1 illustrates one embodiment of the cryogenic apparatus of this invention. In this embodiment the fluid flow path which provides a direct connection between the balancing and the expansion chambers is located external of the refrigerator housing. As shown in diagrammatic fashion, the apparatus comprises a fluid-tight cylindrical housing having movable therein a body 11 with suitable sealing means such as O-ring 12. The movable body in FIG. 1 is a displacer but, as will become apparent in the following description, it may be a piston. In keeping with the common practice the term piston will be used to include a sliding body moving Within a cylindrical vessel which experiences pressure differentials on its surfaces and which responds to changes in the thermodynamic characteristics of the fluid acting upon its surfaces to generate mechanical work. The term displacer will be reserved for a similar body which experiences essentially no pressure differentials on its surfaces and which gencrates and delivers no external work. It will be appreciated that in the following descriptions that when the terms upper and lower are used, they are used only in a relative sense, and that the refrigeration apparatus of this invention may be oriented in any manner. These terms are employed in this description only to correspond to the orientation illustrated in the figures.

In the apparatus of FIG. 1 the movement of displacer 11 defines two fluid chambers of variable volume. The first or upper chamber 14 is the fluid balancing chamber, and the second or lower chamber 15 is the fluid expansion chamber. A shaft 16 is aflixed to the displacer 11, and is connected to a drive means, such as a motor 17.

There are within the refrigerator three fluid flow paths. The first of these fluid flow paths 20 will be seen to pro vide fluid communication between a source of highpressure fluid (in FIG. 1 represented as compressor 21) and the fluid expansion chamber 15. Incorporated in this fluid flow path 20 are an after-cooler 22 (provided with means 23 for introducing a coolant to exchange heat with the compressed fluid), an indirect heat exchanger 24, and a high-pressure inlet valve 25.

The second fluid flow path 30 will be seen to provide fluid communication between the fluid expansion chamber 15 and a low-pressure reservoir illustrated in FIG. 1 to be the compressor 21 which thus combines the highpressure fluid source and the low-pressure reservoir in one apparatus component. Incorporated in this second fluid flow path 30 are a lowpressure exhaust valve 31, a refrigeration load 32, heat exchanger 24 and an auxiliary heat exchanger 36 adapted for indirect heat exchange with the fluid in the balancing chamber 14 as explained below. The operation valves 25 and may be controlled by any suitable means. Exemplary of such means to control these valves are earns 18 and 19 which are mounted on the shaft of motor 17 and which are used to drive valve rods 18a and 19a in the desired sequence.

The third fluid flow path 37 extends between the balancing chamber 14 and the expansion chamber 15, and it incorporates a heat storage means 38 as well as heat exchanger 36.

The operation of the refrigerator of FIG. 1 is illustrated in FIGS. 2A-2D, 3 and 4, the latter being a typical PV diagram for one mode of operation. It will, of course, be appreciated that the PV diagram of FIG. 4 is meant to be illustrative and not limiting.

To begin this cycle assume that the driving mechanism has moved the displacer 11 to its lowermost position, as shown in FIG. 2A. At this point the high-pressure fluid inlet valve 25 is opened to introduce high-pressure fluid, precooled in heat exchanger 24, into expansion chamber 15, and through regenerator 38 into compression chamber 14. The low-pressure exhaust valve is, of course, closed, and high-pressure fluid is permitted to enter chamber 15. The displacer 11 is moved upwardly, increasing the volume of chamber 15 until it has reached, for example, approximately onefifth its maximum volume. At this point the high-pressure inlet valve 25 is closed, and the displacer is continued in its upward motion by driving means shaft 16 and motor 17 to its uppermost position, bringing about additional cooling through expansion of the fluid in chamber 15. When displucer 11 has attained Cir its uppermost position, the low-pressure exhaust valve 31 is opened permitting the fluid to exhaust into the system through the heat exchangers and into compressor 21, thus attaining the final cooling of the fluid. The low-pressure cold fluid remaining in chamber 15 is then swept out of the system into the compressor by moving displacer 11 downwardly. It is preferable, however, that the lowpressure exhaust valve 31 be closed somewhat prior to the attainment of the displacers lowermost position as illustrated at point B in FIG. 4. With the opening again of the high-pressure inlet valve 25, the cycle begins again.

It will be seen that during this cycle the fluid flows back and forth between the balancing chamber and the expansion chamber 15, acting as a heat extraction means. As the fluid in balancing chamber 14 is compressed, it will, of course, be heated, and thus it is necessary to provide means for cooling this fluid and removing the heat of compression, In the apparatus of FIG. 1, this is done through the use of heat exchanger 36 which permits the cooling of the fluid by indirect heat exchange with the low-pressure fluid stream in fluid flow path 31) as it returns into compressor 21. Because a major portion of the work of expansion is extracted in the compressing of the fluid in fluid chamber 14, it is not necessary to provide large cranks or the like and hence there are no large bearings and no wear problems associated with them, Hence, in effect, the balancing chamber takes the place of a large crankshaft and its accompanying wear-susceptible auxiliary components.

In the embodiment shown in FIG. 5, the third fluid flow path is located entirely within the fluid tight housing. In this apparatus there is provided a displacer 40 which has the regenerator 41 located within it. This means that the third flow path is somewhat modified. It is preferably formed of a narrow annular passage 42, defined between the upper end of the displacer 40 and the internal Walls of housing 10, and a series of radial passages 43 communicating between the annular passage 4-2 and the regenerator 41. This arrangement requires some modification also in the second fluid flow path in that the heat exchanger 36 of FIG. 1 is replaced by coils 44 which are in thermal contact with the external wall of fluid tight housing 10. By passing the low-pressure fluid returning to the compressor through these coils 44, it is possible to cool the fluid in chamber 14 subsequent to compressing of the fluid in chamber 14.

FIG. 6 illustrates the use of a pneumatic driving system for the refrigerator of FIG. 1. In this modification the fluidtight housing 10 has a closed extension having movable therein a piston 51 with suitable sealing means 52. The piston 51 is connected with the displacer 11 by means of a shaft 53, and it defines within the housing extension 50 a third, or fluid driving chamber 54. Connected with this third fluid chamber 54 is a fluid line 59 having a first inlet branch line 55, controlled by valve 56 and adapted to introduce highpressure fluid into chamber 54. A second branch line 57, controlled by valve 58, is adapted to connect chamber 54 with the inlet of compressor 21 and thus to provide for fluid exhaust. In the embodiment of FIG. 6. the high-pressure fluid is permitted to flow into chamher 54 when the displacer 11 is to be moved downwardly and maintained at its lowermost position; and the lowpressure fluid line is opened when the displacer is to be moved upwardly and maintained at its uppermost position.

FIG. 7 illustrates the embodiment in which the refrigerator of FIG. 5 is driven pneumatically in a manner somewhat different than FIG. 6. FIG. 7 also illustrates the fact that it is possible to construct an open cycle by providing a separate source of high-pressure fluid 64 and a separate low-pressure reservoir 65, the latter being if desired, the volume surrounding the refrigerator, i.e., the air. If required, some connection between the low-pressure reservoir and high-presssure fluid source may, of course, be made as illustrated by the dotted line 66 which may gencrully be considered to embody a compressor and after cooler, and a clean-up system if desired. The apparatus of FIG. 7 also illustrates that it is possible to provide for the fluid flow in and out of driving chamber 54 by a means not associated with the flow of fluid within the refrigerator itself. Thus, in FIG. 7 there are provided a high-pressure fluid source 67 and a high-pressure line 68 (controlled by valve 69) which connects to conduit '70 leading into chamber 54. There is also provided a lowpressure reservoir 71 and a low-pressure line 72 (controlled by valve 73) in fluid communication with conduit 70. As in the case of the high-pressure fluid source and the low-pressure reservoir associated with the refrigerator, there may be a connection 14 between the high-pressure fluid source 67 and the low-pressure fluid reservoir 71 associated with the driving chamber.

FIG. 8 illustrates another embodiment of a pneumatic driving means for the refrigerator, in this case requiring an additional crank and shaft. In the embodiment of FIG. 8, the displacer has attached to it a piston extension 79 which reciprocates within an open housing extension 78. Sealing means 80 are provided in order to maintain the housing fluid-tight. The piston extension 79 is connected to a crank 81 through a crankshaft 82. Although this arrangement does require means for extracting work from the apparatus, these means may be considerably smaller and simpler than those normally associated with a Claude or Brayton engine.

FIGS. 9-13 illustrate several embodiments of staged refrigerators constructed in accordance with this invention. Such staged refrigerators are particularly suited for attaining very low temperatures and for modification to form liquefiers.

FIG. 9 illustrates one embodiment of the staging of the refrigerator, the basic refrigerator being the design shown in FIG. in which the third fluid flow path is located internal of the fluid-tight housing. In this staged apparatus the first fluid flow path is extended beyond the first ex pansion chamber 15 as path extension 120. This extension of the first fluid flow path passes through the additional indirect heat exchanger 124 and has associated with it a fluid flow control valve 125 between the heat exchanger 124 and the second or colder expansion chamber 115. In like manner the second fluid flow path is extended into extension 130 which has associated with it an exhaust valve 131 and which also passes through heat exchanger 124. Provision is made for cooling two loads 32 and 132 by means of indirect heat exchange with a fluid flowing in conduits 33 and 133. In the arrangement of FIG. '9 there is no fluid communication between the third flow paths of the two stages. Displacer 140 containing regenerator 141 is operated from the same shaft 116 and motor 117 as displacer 41. Cooling of the fluids in balancing chambers 14 and 114 is achieved through an externally circulated fluid coolant introduced into the system through a conduit 98 which has two branches 91 and 92, the first communicating with coils 93 associated with chamber 14 and the second with coils 94 associated with chamber 114. The coolant is removed through a common discharge line 95.

FIG. 10 illustrates a somewhat simpler embodiment of a staged refrigerator constructed in accordance with this invention. In this embodiment the second or colder stage does not incorporate a complete third fluid flow path; rather this stage consists of a fluid-tight housing 110 having a displacer =85 movable therein to define the upper balancing chamber 86 and the lower colder expansion chamber '87. Balancing chamber 86 is in fluid communication through line 88 with balancing chamber 14 of the first stage but is not in direct communication with expansion chamber 87.

A small void volume 89 may be incorporated in expansion volume 87. This void volume changes the shape of the pressure versus volume line (line BC in FIG. 4) for expansion volume 87 so as to more nearly match the P-V diagram which will be described in balancing chamber 110. With the incorporation of void volume 89 better balancing will be obtained and less mechanical work will have to be exchanged with the outside environment. This in turn means that smaller cros'shead mechanisms can be used. Balancing may also be achieved by delaying the closing of valve until slightly after the closing of valve 25 which will increase the size of the P-V diagram of space 87. However, the balancing achieved by this delayed valve closing is not as complete as is the balancing achieved by void volume 89*.

Displacers 48 and 85 in the apparatus of FIG. 10 are moved simultaneously by the same mechanism described above. Cooling of the fluid in the balancing chambers is achieved by introducing a suitable liquid coolant into line 96 which in turn passes through coils 97 in indirect heat exchange relationship with the housing 10 and hence with the fluid in chamber 14. This cooling fluid then passes by means of line 93 through a heat exchanger 99 which permits cooling of the fluid traveling back and forth in the connecting line 88. The arrangement of FIG. 10 has some advantages inasmuch as it does not incur the low-temperature regenerator problems which the apparatus of FIG. 9 does with low-temperature regenerator 141. Therefore, it is possible to obtain colder temperatures in expansion chamber 87 than in expansion chamber 1150f the apparatus of FIG. 9.

FIG. 11 illustrates the incorporation and integration of a Joule-Thomson loop with the staged refrigerator of FIG. 10 in which like numerals refer to like components. In the refrigerator of FIG. 11 there is shown a modification of the means for cooling the balancing fluid. In this modification of FIG. 11 the incoming coolant after passing through coils 97 to cool the fluid is directed by means of line 180 through coils 101 which are in heat exchange relationship with the fluid in chamber 86.

In the arrangement in FIG. 11, the two loads are represented by fluid flowing within a Joule-Thomson loop, and the refrigeration developed by the fluid exhausted from chambers 15 and 87 is used to cool the high-pressure fluid within the Joule-Thomson loop prior to its introduction into a Joule-Thomson heat exchanger and then a Ioule-Thomson valve. Thus, in the equipment in FIG. 11 there is provided a Joule-Thomson loop which consists in this embodiment of a high-pressure branch line connected with the high-pressure line or first fluid flow path 28 of the refrigerator. This high-pressure Joule- Thomson line leads through a main heat exchanger 141 to be cooled by returning low-pressure fluid, then through heat exchanger 32 to be cooled by the cold low-pressure fluiddischarged from chamber 15, then through a second heat exchanger 142, then through heat exchanger 132 to be cooled by the low-pressure fluid discharged from chamber 87, and finally through a Joule-Thomson heat exchanger 143. The cold high-pressure fluid is then passed through a Joule-Thomson expansion valve 144 into a low-pressure reservoir 145 which may or may not contain liquefied gas. The low-pressure cold fluid is then taken through a low-pressure line 146 which passes up through heat exchangers 143, 142 and 141 finally to be discharged into the second fluid flow path 30 to the low-pressure side of compressor 21. As shown by the components indicated in dotted lines, it may be optionally desirable to return the low-pressure fluid from the Joule-Thomson loop by way of a bypass line 148, an auxiliary clean-up system 149 and a booster compressor 150. It is also within the scope of this invention to provide completely separate high-pressure fluid sources and low-pressure reservoirs for the refrigerator and for the Joule-Thomson loop, making it possible if desired to use two different fluids.

FIGS. 12 and 13 illustrate yet another modification by which staging may be accomplished in the refrigerator of this invention. In FIG. 12 the third fluid flow path is located within the refrigerator while in FIG. 13 it is external of the refrigerator. In the modification shown in FIG. 12, a single enclosure housing is provided which is made up of coaxially aligned integrated sections 155, 156 and 157. The displacer within the housing is also formed of joined or integrated sections which are coaxially aligned and appropriately sized for the enclosures in which they operate, these sections being numbered 158, 159 and 1611. Within the housing there are defined a balancing chamber 161 and three successively colder refrigeration chambers 162, 163 and 164. Cooling of the fluid in the balancing chambers 161 is achieved by circulating an appropriate coolant through coils 165, the coolant being introduced through line 166 and discharged through line 167.

The third fluid flow path of the apparatus of FIG. 12 is essentially the same as that shown for the apparatus in FIG. 5. However, it will be noted that a regenerator is provided for only the first displacer section, a modification which is comparable to that of FIGS. and 11. This regenerator 168 is positioned within the first or upper displacer section 158 and has a series of upper radial paths 169 and lower radial paths 16% for circulating the fluid through the regenerator 168 between balancing chambers 161 and the first refrigeration chamber 162. In an arrangement such as shown in FIG. 12 it is necessary to provide suitable sealing means to isolate chambers 162, 163 and 164. It is Within the skill of the art to choose among the various well-known sealing means.

As in the apparatus of FIG. 10, the two refrigeration chambers 163 and 164 of FIG. 12 have small void volumes associated with them for the reason previously de scribed. Void volume 152 associated with chamber 163 may take the form of an annular ring 152 or a series of individual volumes; while void volume 153 associated with chamber 164 may be similar to volume 89 of FIG. 10.

FIG. 12 also shows the refrigeration device being used as a means of cooling a Joule-Thomson system. However, the arrangement of Joule-Thomson heat exchangers is different from that shown in FIG. 11. The apparatus of FIG. 12 may be used either as a refrigerator or a liquefier since it incorporates a Joule-Thomson valve and the necessary additional heat exchange means to accomplish liquefaction. The first high-pressure flow path 170 has branch lines 171, 172 and 173 communicating with refrigeration chambers 162, 163 and 164, respectively. Each branch line has a valve (174, 175 or 176) associated with it to control the flow of fluid therethrough. It will be seen that integrated into the high-pressure flow path are a series of successively colder heat exchange means, shown diagrammatically as heat exchangers 180186. In practice, heat exchangers 181185 would normally be a single heat exchanger with connections being made at the appropriate temperature levels.

Rather than direct all of the high-pressure fluid into the refrigerator, a portion of the cold high-pressure fluid is withdrawn through line 187 and directed through heat exchanger 185, then through Joule-Thomson heat exchanger 186 and finally through a Joule-Thomson expansion valve 190. Any liquid is collected in reservoir 191.

The second, or low-pressure, fluid flow path 195 extends from the reservoir 191 through all of the heat exchangers 186180 and in accordance with the requirements for the apparatus of this invention, it has a series of branch lines 196, 197 and 198 in fluid communication with refrigeration chambers 164, 163 and 162, respectively. Fluid flow control valves 200, 201 and 202 are associated with these branch lines. The apparatus of FIG. 12 provides a compact refrigerator or liquefier as desired, and in its arrangement of heat exchange means and use of the three flow paths and balancing chamber it represents a highly eflicient device.

The modification in FIG. 13, in which like numerals refer to like components in FIG. 12, has an external third paratus of FIG. 13 is adapted to deliver refrigeration to an external load, e.g., to a Joule-Thomson loop as in MG. ll. The high-pressure fluid llow path comprises line 215 (connected to a high-pressure fluid source not shown) and branch lines 216, 217 and 218 having valves 219, 220 and 221, respectively. The low-pressure fluid flow path 225 has branch lines 226, 21 7 and 228, the flow in which is controlled by valves 229, 2.30 and 231. Heat exchangers 35, 36 and 37 provide the required indirect heat exchange between the fluids in the two paths; while heat exchangers 238, 239 and 246 represent refrigeration loads, e.g., the high-pressure fluid of a Joule-Thomson loop.

It will be apparent to those skilled in the art that a number of modifications including driving means, connections to various types of thermal loads and the like are all possible within the scope of this invention.

ln the operation of any of the staged apparatus as illustrated in FIGS. 9 through 13, it is necessary to control the operation of the high-pressure inlet valves and the low-pressure exhaust valves so that they operate essentially simultaneously for each of the refrigeration chambers used. Thus, for example, in the apparatus of FIG. 12 it is necessary that highpressure inlet valves 174, and 176 operate in unison as well as the low-pressure exhaust valves 200, 201 and 202. They will, of course, follow the same general cycle as illustrated in the tabulation in FIG. 3.

It will be seen from the above description and drawings that the cycle and apparatus of this invention combine the use of indirect heat exchangers in conjunction with a Giflord-McMahon type refrigerator which has a displacer moving within a fluid-tight housing and a fluid flow path containing heat storage means connecting the two chambers defined within the housing. The use of the fluid chamber 14 as a balancing or compression chamber means that far less mechanical energy must be extracted from the system by a crank and shaft, thus making it possible to use much simpler, smaller and more reliable equipment for this purpose. Moreover, the use of the indirect heat exchange system for the main fluid stream which is circulated within the refrigerator means that the void volumes within the apparatus are maintained at a minimum, and hence the efliciency may be maintained at a high level. It will also be seen from the above drawings that the refrigerator is highly flexible with regard to the way in which it may be driven, the heat exchange means which can be used for cooling the fluid in the balancing chamber, and with respect to the equipment with which it may be integrated, e.g., a Joule-Thomson loop.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efliciently attained, and since certain changes may be made in carrying out the above method and in the construction set forth without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. A cryogenic apparatus. comprising in combination (a) fluid-tight cylindrical housing means;

(b) a body movable within said cylindrical housing means thereby to define (c) fluid balancing chamber means and refrigeration chamber means the volumes of which are determined by the motion of said movable body;

(d) a source of high-pressure fluid;

(c) low-pressure reservoir means;

(t) first fluid flow path means providing fluid communication between said source of high-pressure fluid and said refrigeration chamber means;

(g) second lluid flow path means providing fluid communication between said low-pressure reservoir means and said refrigeration chamber means;

(h) third fluid flow path means providing fluid communication between said fluid balancing and said refrigeration chamber means and incorporating heat storage means;

(i) first and second fluid flow regulating means incorporated in said first and second fluid flow path means, respectively;

(j) primary heat exchange means adapted to effect indirect heat exchange between fluid flowing in said first and second flow path means and located between said first and second fluid flow regulating means and said source of high-pressure fluid and said low-pressure fluid reservoir means;

(k) auxiliary heat exchange means adapted to effect indirect heat exchange with fluid in said first fluid chamber means; and

(1) means to control the movement of said movable body and the operation of said first and second fluid flow regulating means.

2. An apparatus according to claim 1 wherein said source of high-pressure fluid and said low-pressure reservoir means are combined in the form of a fluid compressor.

3. An apparatus according to claim 2 further characterized by having an aftercooler means in said first fluid flow path.

4. An apparatus according to claim 1 wherein said lowpressure reservoir means comprises the surroundings around said apparatus and the cryogenic apparatus is an open-cycle device.

5. An apparatus according to claim 1 wherein said auxiliary heat exchange means is an integral part of said second fluid flow path whereby the fluid flowing therein is used to cool fluid circulated in said third fluid flow path.

6. An apparatus according to claim 1 wherein said third fluid flow path means and said heat storage means are located external of said housing, and said auxiliary heat exchange means comprises a separate heat exchanger.

7. An apparatus according to claim 1 wherein said third fluid flow path means and said heat storage means are internal of said movable body and said auxiliary heat exchange means comprises fluid flow coils in heat exchange relationship with that portion of the external wall of said cylindrical housing substantially corresponding to the maximum volume of said first chamber means.

8. An apparatus according to claim 7 wherein said third fluid flow path includes (1) an annular passage defined between the internal 'wall of said housing and a portion of the wall of that end of said movable body which defines said first chamber means, and

(2) radial fluid passages communicating between said annular passage and said heat storage means.

9. An apparatus according to claim 1 wherein said means to control the movement of said movable body. comprises a shaft and motor means connected thereto.

10. An apparatus according to claim 1 wherein said means to control the movement of said movable body comprises a driving piston mechanically linked to said movable body and means to impart motion to said driving piston.

11. An apparatus according to claim 10 wherein said means to impart motion to said driving piston comprises means to apply and release fluid pressure on said driving piston.

12. An apparatus according to claim 1 wherein said auxiliary heat exchange means comprises a heat exchanger adapted to effect indirect heat exchange between fluid flowing in said second flow path and fluid within said first chamber means.

13. A cryogenic apparatus, comprising in combination (a) a plurality of fluid-tight cylindrical housing sections;

'(b) a body movable within each of said cylindrical housing sections;

(0) variable-volume fluid balancing chamber means in at least the first housing section;

(d) a variable-volume refrigeration chamber in each of said housing sections;

(e) a source of high-pressure fluid;

(f) a low-pressure reservoir;

(g) first fluid flow path means providing fluid communication between said source of high-pressure fluid and each of said refrigeration chambers;

(h) second fluid flow path means providing fluid communication between said low-pressure reservoir and each of said refrigeration chambers;

(i) third fluid flow path means providing fluid com munication between said balancing chamber means and the refrigeration chamber in the same housing section, said third fluid flow path means incorporating heat storage means;

(j) first and second fluid flow regulating means associated with each of said refrigeration chambers and incorporated in said first and second fluid flow path means, respectively;

(k) primary heat exchange means adapted to effect indirect heat exchange between fluid flowing in said first and second flow path means;

(1) auxiliary heat exchange means adapted to effect indirect heat exchange with fluid in said balancing chambers;

(in) means to control the movement of said movable bodies; and

(11) means to control all of said first fluid regulating means and all of said second fluid flow regulating means.

14. An apparatus according to claim 13 wherein said source of high-pressure fluid and said low-pressure reservoir are combined in the form of a fluid compressor.

15. An apparatus according to claim 13 wherein said housing sections are separate fluid-tight enclosures.

16. An apparatus according to claim 15 wherein only the first of said movable bodies contains heat storage means and the refrigeration chambers within those of said enclosures other than said first enclosure are not connected with said third fluid flow path means.

17. An apparatus according to claim 16 wherein said refrigeration chambers within those of said enclosures other than said first enclosure have void volumes associated therewith.

18. An apparatus according to claim 15 wherein each of said movable bodies contains heat storage means and that portion of said third fluid flow path associated with each of said enclosures is internal of said enclosures.

19. An apparatus according to claim 13 wherein said housing sections comprise a single enclosure of stepped configuration and said movable bodies are joined and are of stepped configuration, whereby a single balancing chamber is provided.

20. An apparatus according to claim 19 wherein said third fluid flow path is internal of said apparatus and extends only between said single balancing chamber and the first or warmest of said refrigeration chambers.

21. An apparatus according to claim 20 wherein said refrigeration chambers other than said first refrigeration chambers have void volumes associated therewith.

22. An apparatus according to claim 13 having indirect heat exchange means associated with said second fluid flow path means, said heat exchange means being adapted for delivering refrigeration to a refrigeration load.

23. An apparatus according to claim 22 wherein said refrigeration load comprises a high-pressure fluid stream circulating in a Joule-Thomson loop.

24. An apparatus according to claim 23 wherein the fluid circulating in said first and second fluid flow path means is also the fluid in said Joule-Thomson loop.

25. A method for developing refrigeration, comprising the steps of (a) supplying a first stream of high-pressure fluid to an expansion chamber of variable volume;

(b) exhausting a second stream of low-pressure fluid from said expansion chamber subsequent to expansion of said high-pressure fluid therein;

(c) exchanging heat between said first and second streams;

(d) extracting at least a portion of the work of said expansion by compressing fluid within a balancing chamber, the volume of which is variable and complementary to that of said expansion chamber;

(e) circulating fluid between said balancing chamber and said expansion chamber as their volumes vary;

(f) storing refrigeration during that part of the cycle when fluid is transferred from said expansion chamber to said balancing chamber and employing said stored refrigeration to cool said fluid when it is transferred from said balancing chamber to said expansion chamber; and

(g) extracting the heat of fluid compression from said fluid circulated between said balancing chamber and said expansion chamber.

26. A method according to claim 24 wherein said extracting heat of fluid compression comprises effecting indirect heat exchange between said fluid circulated between said balancing and expansion chambers and said second stream of low-pressure fluid.

27. A method according to claim 24 wherein said extracting heat of fluid compression comprises effecting indirect heat exchange between said fluid circulated between said balancing and expansion chambers and a separate fluid coolant stream.

28. A method for developing refrigeration, comprising the steps of (a) supplying a first stream of high-pressure fluid to a series of expansion chambers of variable volume and successively lower temperatures;

(b) exhausting a second stream of low-pressure fluid from said expansion chambers subsequent to expansion of said high-pressure fluid therein;

(c) exchanging heat between said first and second streams;

(d) extracting at least a portion of the work of said expansion by compressing fluid within at least one balancing chamber associated with at least the first of said expansion chambers; the volume of each of said balancing chambers being variable and complementary to that of its associated expansion chamber;

(e) circulating fluid between each of said balancing chambers and its associated expansion chamber as their volumes vary; and

(f) extracting the heat of fluid compression from said fluid circulated between said balancing chambers and said expansion chambers.

29. A method according to claim 27 including the step of delivering refrigeration to a load through indirect heat exchange between the low-pressure fluid in said second stream and a load comprising a high-pressure fluid stream circulating in a Joule-Thomson loop.

References Cited UNITED STATES PATENTS WILLIAM J. WYE, Primary Examiner 

